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Passive NO Adsorption on Hydrothermally Aged Pd-Based Small-Pore Zeolites |
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| Authors: | Shan Yulong Sun Yu Li Yaobin Shi Xiaoyan Shan Wenpo Yu Yunbo He Hong |
| Affiliation: | 1.State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China ;2.Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China ;3.University of Chinese Academy of Sciences, Beijing, 100049, China ; |
| Abstract: | Pd-based small-pore zeolites with different framework structures (AEI, CHA and RTH) were synthesized by a facile incipient wetness impregnation method. The zeolites were utilized as low-temperature passive NOx adsorbers (PNA) for NOx storage before and after hydrothermal aging. It was found that 1 wt% Pd/AEI showed better PNA behavior than the 1 wt% Pd/CHA and Pd/RTH samples, regardless of hydrothermal aging at 750 and 800 ℃. The AEI zeolite has a three-dimensional but tortuous pore channel structure, which accelerated Pd dispersion at 750 ℃ but inhibited Pd aggregation at 800 ℃ when subjected to hydrothermal aging. Pd/CHA showed a slight increase in Pd dispersion at 750 ℃, but extensive Pd aggregation at 800 ℃ due to its straight and unhindered three-dimensional pore structure. The Pd species in Pd/RTH zeolite were prone to accumulation during hydrothermal aging due to the two-dimensional pore structure. Therefore, Pd/AEI can be utilized as an efficient and stable PNA after activation by mild hydrothermal aging treatment. |
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